Chalermchat Manop

Laboratory digital signal analysis with virtual spectrum analyzer

This paper present laboratory digital signal analysis with virtual spectrum analyzer which is created using LabVIEW program on digital oscilloscope TDS 5054. This research aims to develop a knowledge-base on digital signal analysis and the working of virtual instrumentation, a topic which is currently attracting wide interest due to its many good attributes including flexibility, modularity, and low cost. It also aims to make a good use of expensive digital oscilloscope TDS 5054. In this study, laboratory spectrum analysis is performed with variable sampling rate, effect of windows filter etc. The results are displayed by both time domain and frequency domain. There are samples of signal waveforms such as sinusoidal waveform, square waveform, six-step waveform, and PWM (pulse width modulation) waveform. These waveforms are important in the study of power electronics. The data are obtained using special module program to extract information from the digital oscilloscope

Fault detection and protection of three-phase induction motor using Eigen based analysis

This research presents the design and the implementation of a system for detecting and preventing external faults of 3 phase induction motor using Eigen based analysis, in order to prevent faults in various pattern and reduce the complexity of data processing. The 6 inputs are composed of three-phase voltage and current signals for the induction motor. These inputs will be calculated for the root mean square values before the Eigen based analysis and Euclidean Distance calculation. These values are comparable to which of the normal condition of the induction motor, in order to identify the faults in 6 conditions of Single Phase, Over Voltage, Under Voltage, Over Load, Unbalance Voltage and Locked Rotor. The software is designed by MATLAB program connecting with the DAQ card for controlling the 6 signal inputs receiving and sending an output signal to control power supply relay to the induction motor. After the experiment under the various loading conditions was conducted, the system can detect and prevent...

A study of performance and comparison of VSI with improved current waveshape for three-phase rectifier

This paper studies and compares the efficiency of voltage source inverter with traditional 3-phase rectifier direct current circuit on the front end, with passive filter, and with improved current wave shape. The efficiency evaluation is tested using THD, power factor and under changing modulation index, switching frequency and changing load. There is also a comparison of the effect of delta modulation switching technique and SPWM method on direct current circuit.

Stator faults detection based on the dq0 voltage components

This paper presents the technique for detection of shorted turns in stator winding of induction motors. The strategy is based on the dq0 voltage components. The proposed technique determines dq components of time domain of harmonics obtained from Park transformation instead of the stator phase voltage. Zero component (0) is calculated from the fundamental voltage excitation only. In the testing, the supply is sinusoidal waveform and the motor must be star connected with floating neutral. From experimental results, pattern of dq0 voltage components in order to use for the stator faults detection is possible.

A low cost prototype for testing stator winding shorted turns in 3-phase induction motors

This paper presents a prototype of stator winding shorted turns detector for three-phase induction motors. The focus condition is turn-to-turn short circuit, because this condition is the initial problem. The diagnosis technique is detectable from the voltage sum of the three instantaneous line to star-point voltage. In the testing, the supply is sinusoidal waveform and the motor must be star connected with floating neutral. Before diagnosis, this instrument will also determine the level of supply voltage imbalance, if it is over the limit, the test instrument will not diagnose shorted turns. From experimental results, 3-hp and 5-hp induction motors were used for testing this equipment which is capable of accurately identifying percentage of stator winding shorted turns